Nailfold videocapillaroscopy abnormalities in autoimmune inflammatory myopathy subsets

Nailfold videocapillaroscopy (NVC) alterations have been described in autoimmune inflammatory myopathies (AIM). This study aimed to describe NVC abnormalities in AIM subsets using a clinico-sero-pathological approach.

We studied subjects from the Canadian Inflammatory Myopathy Study (CIMS), a prospective AIM cohort. NVC images were acquired using the DS MEDICA Videocap (×200 magnification). Capillary density was scored quantitatively and semi-quantitatively. Ectasias, giant capillaries, ramified capillaries and microhaemorrhages were scored as present or absent and with a standardized semi-quantitative scale (0 = none, 1=≤33%, 2 = 33-66% and 3=≥66% abnormal capillaries/total capillaries per mm). NVC patterns (i.e. scleroderma early/active/late, scleroderma-like, non-specific and normal) were described. NVC features and patterns were compared between AIM subsets.

We included 99 AIM subjects: 41 dermatomyositis, 24 scleromyositis, 16 anti-synthetase syndrome, seven immune-mediated necrotizing myopathy, eight inclusion body myositis and three polymyositis. A total of 71% were female, and the median disease duration was 1 year [IQR; 0.4-2.8]. The most frequent NVC abnormality was decreased capillary density in dermatomyositis (95%), scleromyositis (92%) and anti-synthetase syndrome (87%). Qualitatively, 44% of subjects had abnormal NVC, 25% non-specific NVC abnormalities and 30% normal NVC. NVC patterns were not discriminant between dermatomyositis, scleromyositis and anti-synthetase syndrome. NVC abnormalities were absent in immune-mediated necrotizing myopathy, inclusion body myositis and polymyositis.

Dermatomyositis, scleromyositis and anti-synthetase syndrome showed frequent NVC abnormalities, although no NVC pattern was associated with a particular subset in our study. However, NVC may help distinguish between these subsets and immune-mediated necrotizing myopathy, inclusion body myositis and polymyositis.